better borrow from banks than family members, even if your MIL is fine with it now, can you be sure that she won't be in a few years or months time?

treat the interest from banks as punishment for your mistake, will make you more cautious in your future investment, now it seems you are being bailed out with minor repercussion.

with your mindset (MIL are able to afford it), can you make certain that you won't do the same mistake again?